ALDOT Director John Cooper said one girder was damaged by extreme heat from the burning plastics which melted out of one of the two 18-wheeler trucks involved in the crash. The other vehicle carried petroleum.

"Bridges are constructed of steel and concrete and both of those have some susceptibility to extreme heat," Cooper said. "If you expose either one of those to extreme heat there is some risk of damage."

View full sizeOfficials with the Alabama Department of Transportation released this image of the detour routes around an 18-mile span of the General W.K. Wilson Jr. Bridge, which was damaged after a fiery crash on Thursday, May 22, 2014. (Courtesy of the Alabama Department of Transportation)

Officials expect one northbound lane of Interstate 65 between exits 19 and 31 to reopen by or before 3 p.m. Sunday. Final repairs are not expected to be completed until later.

The closure is expected to cause headaches for Memorial Day travelers heading north for the long weekend.

"There would never be a good time for something like this to happen, but certainly a holiday weekend creates additional stresses and strains," Cooper said. "We are straining our system on holiday weekend(s) anyway, under good conditions."

He asked for the public's patience as work continues.

"This is nobody's fault," he said. "Everything that can be done is being done. Our people are on this. We've dealt with these situations before, we know how to do this, but it'll take some time."

Vince Calametti, ALDOT's Ninth District chief engineer, said crews have been working around the clock to clear and assess damage. One of the main focuses on Friday afternoon was getting signs placed to warn motorists of the detours around the closed 18-mile span of the bridge.

He said multiple crews were dealing with the aftermath, including ones from other areas around the state.

The Salvation Army of Coastal Alabama has sent a canteen to provide food and water to workers on the bridge, known locally as the Dolly Parton Bridge. On Thursday, the organization provided relief to 150 first responders and emergency officials, said spokeswoman Katie Emer.

"These crews are working tirelessly in this summertime heat, plus, there really is no easy way for them to get to food or water," she said.

The Salvation Army plans to stay on-site through the weekend as needed.

Cooper said a plan to complete repairs will be drawn up within two to three weeks. After that it will go out to bid and a contractor will be chosen for the work. That process should be completed within 10 days of the call for bids, Cooper said.

During the work, traffic will be partially reversed in the southbound lanes to accommodate northbound vehicles.

"To reverse the traffic takes some engineering and some construction," Cooper said. "It's not just a matter of getting (traffic) to go the other way. You have to provide a means for it to crossover."

Repairs will be paid for with federal funds, according to officials.

Alabama State Troopers said one person, who was driving the truck filled with plastics, died after he failed to stop when the truck in front of him braked for another crash.

Troopers did not provide additional details on the crash which stopped the truck.